Question

How many 6-digit telephone numbers can be constructed using the digits 0 to 9, if each number starts with 67 and no digit appears more than once?

Answer 1

Correct Answer - `4^(6)`
The first ring can be worn in any of the 4 fingers. So, there are 4 ways of wearing it.
Similarly, each of the other rings can be worn in 4 ways.
So, the required number of ways `=(4xx4xx4xx4xx4xx4)=4^(6).`